Atlantic Multi-Decadel Oscillation
This is a web page put out by NOAA that shows an index value of the theoretical AMO: http://www.aoml.noaa...ift/amo_fig.php
There are some good links on this web page. There is also a good explanation of the AMO with more links from Wikipedia: http://en.wikipedia....dal_Oscillation
This provides references and links to information on the AMO.
Scientists have recently discovered the AMO and PDO and some scientists have linked the dry weather of the 1920s and '30s in the central U.S. to changes in these two indexes. While the PDO trended negative in the 1900s through 1910s, it was moving back towards positive during the 1920s and 30s while the AMO did the same. The drought that led to the dust bowl started in the 1920s and lasted through the mid 1930s. During the mid 40s, the PDO moved back to a negative phase and remained there until the mid 1970s. The AMO went from positive to negative in the mid 1960s and remained negative until the mid 1990s, when it returned to positive. Right after this, the PDO was negative, but has not shown a strong trend towards a negative phase, though we could be too early into it to really tell.
So, putting the two together with precipitation trends in the upper midwest:
1910s: AMO: Negative PDO: Neutral-Negative
Precip: Drying trend from wet conditions
1920s: AMO: Negative to Positive in 1925 PDO: Negative to Positive
1930s: AMO: Postive PDO: Positive
1940s: AMO: Positve PDO: Positive to negative late in decade
1950s: AMO: Positive PDO: Negative
1960s: AMO: Positive to negative mid-decade PDO: Negative
Precip: Becoming wetter
1970s: AMO: Negative PDO: Negative to Positive mid-decade
Precip: Becoming wetter
1980s: AMO: Negative PDO: Positive
Precip: Wet (drought late in decade)
1990s: AMO: Negative to positive mid-decade PDO: Positive to negative late decade
2000s: AMO: Positive PDO: ????
Precip: Wet with a drying trend
I put ???? for the PDO during this decade because despite a very negative index from 1998-2002, positive values returned from 2003-2007. With the oncoming La-Nina, however, the PDO could return to a negative value, and we don't know where it will go from there. The last switch from positive to negative in the '40s did see some jittering around before it finally stuck in the negative phase.
Also of note: Sea ice extent in the arctic peaked in the late 1940s and early 1950s, when the PDO was strongly negative and the AMO was strongly positive. The effect that this has on sea ice, we don't know, but with a positive AMO and a negative PDO in the late 1990s and early 2000s surely did not stop sea ice extent from declining, so I would guess that there is something else affecting it.
It appears Sam Jowett, Metragirta and you have much in common. Over in the General Weather Chat discussion forum Sam is attempting to track the relationship of the month of October has to predicting the following winter of the UK. The issue appears to be related to the dataset bing too limited to have sufficient indications of anything more then either a random pattern and a small allusion to dry Octobers (Low Soil Moisture Content) can relate to cooler then normal winters.
At the same time in the Climate Discussion and Analysis forum Metragirta is trying to establish the relationship of the ENSO to the AMO. Snowhope had suggested that there might be some work done that demonstrates an association between all the various large scale weather patterns and recorded phenomena. I did a little research and found that the idea of trying to establish a interdependent relationship is a relative new science.
At the most a Dr. Wang at the University of Hawaii appears to have done some preliminary analysis and in the second study I added in response to snowhope ( http://iprc.soest.ha..._Carton4agu.pdf ) on page 13 of 19. Here there are three graphs the relationship of El Nino to the North Atlantic and the North Pacific seemed to begin to demonstrate an interesting change since about 1965. Where as before then there did not appears to be a interrelationship, after 1969 there appears to be an inverse relationship between the North Atlantic and North Pacific basin patterns.
The question for me starts to become one of how and why did this interrelationship develop. I cannot understand how added atmospheric energy from an increased atmospheric gas entropy could effect the development of what appears to be standing waves in the atmospheric Rossby barometric or Klein gravity waves. So when we go back and attempt to put this into perspective with the Arctic ice floe breakup it would appear that there may not be a relationship between the ENSO as much as there is a relationship between the development of standing waves and the change in the Arctic or Northern NH Jet Stream.
I wonder if you had considered that the four of you maybe spearheading the newest opportunity for research?
Hi, BR Short:
As you say there are a lot of papers concerning AMO and PDO influences in US temperatures and precipitations. You must consider that PDO, still positive, has probably started to switch to its negative phase some about between 1987 and 2000. You only have to apply an 11 year filter to data and you will see it clearly.
About this inverse relationship between AMO and PDO you say:
It could be Termohaline circulation. It is said that while North warms, South cools. If you see termohaline circulation, in the Atlantic we have superficial waters, with a long time receiving a solar influence. But in the Pacific there is mixture of waters: those coming with MOC, and also superficial waters. There is no solar signal for Pacific. As those deep waters are transported by MOC, they really come from the south and are cooler, that could explain that inverse relationship.
In this two graphs you can see AMO and PDO reconstructions and its linear trend. AMO is warming since 1567 (Gray 2004), the whole period of reconstruction. PDO is cooling since 1661(Biondi 2001), once again the whole period. But if you look to the other reconstruction of PDO for the last millennia (MacDonald &Case 2006), you will see that between 990 and 1450 PDO was warming and after that its starts cooling. So I think in THC with AMO having a solar signal and a good coherence with actual global temperatures and PDO a remote signal of AMO, and all the interchanges of MOC and THC in its way to the Pacific. In consequence PDO has a weak coherence with actual temperatures and no solar signal.
The issue I have with the surface Southern Ocean Oscillation is the lack of discussion of the rise of the cool THC deposits rising out of the Marianna's Trench off the coast of Japan. As cooler THC waters move along the bottom of the ocean basin to fill the Trench, the not as cool reservoir begins to over top the sides of the Trench where it seeps across the Southern Ocean Basin floor until it encounters the cooler waters falling off the Western Antarctic Peninsula causing a localized thermal turnover or stirring of the deep ocean waters which then exits the Southern Pacific basin and then enters the Southern Atlantic basin where it drifts northward.
The question is if the waters that are exiting the Marianna's are the warmer waters that had been deposited in the 1300's or is the Marianna's overflow a non-player in the apparent warming trend? It is clear that there are major pattern variations, the problem is trying to discern the drivers of them. The observation of the inversion I had made was of the Northern Pacific SSTs when compared to the Northern Atlantic SSTs and not the ENSO and NAO. In short, the observations that I was attempting to make was that the northern patterns appears to be inversions of each other. When you look at the intrusion of the warm waters into the Arctic region it appears that they are coming from one or the other; but, rarely both at the same time, except during a year of transition. It appears that during those years of transition that the depth of Arctic melt is excessive. Extending this observation, it makes sense to consider whether or not this could be a characteristic of the Northern Oceans as opposed to the Southern Oceans.
The issue is the lack of depth of knowledge of the drivers of the patterns and why there appears to be a see-saw balance between the two, I would think that most of the driver is due to the heat engine effect and the restricted entries to the Arctic Ocean basin act like valves restricting the fluid dynamic flow. If you have a period of cold Arctic temperatures, the THC deep current should increase in flow rate and during periods of warmth the flow rate should decrease, regardless of the effect of the fresh water pools existing directly next to highly saline surface pools. The question is whether or not the variations in temperature or Relative Humidity of the Arctic Atmosphere is what drives both the Arctic Ocean current flow rates or the over turning of the deep ocean currents causing the change in the flow direction?
I suspect that the Specific Humidity is the primary driver; however, I do not have data to support this idea. (Keeping in mind without observational data it is improper to state a scientific hypothesis.)
Looking at your graphs in association to the patterns versus the date the two have a similar pattern and not the opposite pattern you would get on first look. It suggests that the PDO and AMO have a similar pattern. What I am curious about is the NAO near the Arctic Circle as opposed to the NPO.